Electric feed mechanism for planers and current-controlling system therefor



S. P. JOHNSON. ELECTRIC FEED MECHANISM FOR PLANERS AND CURRENT CONTROLLING SYSTEM THEREFOR.

APPLICATION HLED MAR. 16, 1916. 1,342,915. Patented June 8, 1920.

5 SHtElS-SHEET 1. I

511m Jor znson S. P. JOHNSON.

ELECTRIC'FEEDY-MECHANISM FOR PLANERS AND'CURRENT CONTROLLING SYSTEM THEREFOR.

Patented June 8, 1920.

APPLICATION FILED MAR.16, I916.

5 SHEETS-SHEET 2.

m M J P W 5 2 E23 M5.- Wm

S. P. JOHNSON. ELECTRIC FEED MECHANISM FOR PLANERS AND CURRENT CONTROLLING SYSTEM T HEREFOR.

Patented June 8, 1920.

APPLICATION FILED MAR-16, 1916.

5 SHEETS-SHEET 3.

J5 J5 J7 Imenkn S. P. JOHNSON. ELECTRIC FEED MECHANISM FOR PLANERS AND C URRENT CONTROLLING SYSTEM T HEREFOR.

Patented June 8, 1920.

APPLICATION FILED MAR. I6, I916.

5 SHEETSSHEET 4.

S. P. JOHNSON.

ELECTRIC FEED MECHANISM FOR PLANERS AND CURRENT CONTROLLING SYSTEM THEREFOR.

APPLICATION FILED MAR. I6. I916.

Patented June 8, 1920.

. 5 SHEETSSHEET 5.

IWW 572, 1 P J571n60n/ Z 3 MSW:

UNITED STATES PATENT OFFICE.

SVEN P. JoHNsoN; or PHILADELPHIA, PENNSYLVANIA, ASSIGNOR T0 NILES- BEMENT-PQND, COMPANY, or JERSEY CITY, NEW JERSEY, A CORPORATION v v0F NEW JERSEY.

ELECTRIC FEED MECHANISM FOR PLANERS AND CURRENT-CONTROLLING SYSTEM THEREFOR.

To all whom it may concern:

Be-it known that I, SVEN P. JOHNSON, a citizen of the United States, residing in Philadelphia, Pennsylvania, have invented Electric Feed Mechanism for Planers and Current-Controlling System Therefor, of which the following is a specification.

The invention relates to a planer feed mechanism which comprises an electric motor suitably connected with the tool head or tool heads of the planer and adapted to be operated automatically from time to time to effect the moving of the tool heads and the feeding of the tools. The mechanism embodying the invention is especially intended to replace the gearing and ratchet and pawl mechanisms commonly employed for effecting automatic feeding. n

One object of this invention is to provide a novel combination of elements primarily intended to so control the electric current in the motor circuit that after flowing for a predetermined time it will be automatically cut off. The apparatus includes an adjustable element whereby the time during which the current flows may be varied between wide limits. I

More particularly it is desired to provide a system for accurately predetermining the time or extent of the operation of the electric motor.

A further object of the invention is to provide a substantial, reliable and relatively Simple form of motor actuated switch, together with novel controlling means therefor. These obj ectsa'nd other advantageous ends I secure as hereinafter set forth, reference being had to the accompanying drawings, in which I have shown the embodiment of the invention which I now deem preferable. It willfbe understood, however, that the drawings are intended for illustrative purposes only and that various departures from the embodiment illustrated may be made without departing from the spirit of the invention as set ,forth in the. appended claims.

Of the drawings Figure 1 is a diagrammatic view illustrat- Specification of Letters Patent.

Patented June 8, 1920.

Application filed March 16, 1916. Serial No. 84,696. I

' ing a mechanism constructed in accordance with my invention Fig. 2 is a plan, partly in section, of the controller box and certain of the associated elements;

Figs. 3 and L are vertical sections on the lines aa and c0, Fig. 2;

Fig. 5 is a horizontal section on the line bb, Fig. 3;

Figs. 6 and 7 are respectively an elevation and an inverted plan of one of the motor controlled switches;-

Fig. 8 is a perspective view of the safety switch;

Fig. 9 is an elevation of the buffer for the safety switch with certain of its associated apparatus.

Referring particularly to the diagrammatic Fig. 1 of the drawings, 6 represents conventionally the reciprocating table of a planer of any usual or preferred construction. The planer is provided with one or more tool heads which are adapted to carry cutting tools and which are mounted adjacent the table in'any suitable way so as to be capable of movement to effect feeding of the tools transversely of the lines of travel of the table. A single tool head is conventionally indicated at 6. For moving the tool head there is provided a motor 8, the motor being connected with the tool head by any suitable mechanical connection such for instance as the screw conventionallyindicated at 8. y

1 represents a pilot switch designed to be, periodically operated by any desired means such as a dog 5 on the reciprocating table 6 of the planer. and so made that its movable contact 2 tends to remain in a neutral or off position, from which it is moved by and stopped. Preferably the controlling circuit is so arranged asv not to receive the the Winding 13 is' deenergized, the core 12,

main current of the motor but is adapted to act through a suitable relay mechanism. As illustrated, one terminal of the armature is connected directly with'the line 10 and the other is connected with the movable core 12 of a solenoid 12. J The solenoid has a winding 13 which is in the motorcontrolling circuit to be more fully described hereinafter, and when the winding is energized,"

the core is lifted into engagement with a fixed contact 14 connected with the line 11. In this way the main motor circuit is completed andthe motor is started. When ,closed' Preferably also there is a supple- 'mental safety switch 19, the purpose of 1 to be presently described.

5' which will be fully set forth hereinafter. In

operation the motor8 is started when the switch 2 is closed by the engagement therewith of the dog 5, and the motor is stopped when the switch 18 is opened in the way For opening the "switch 18 at the'proper time, there is provided an operating member which is actuated by means mechanically .and electrically independent of the motor 8. As illustrated, this member consists of a rotatably mounted disk 29-carrying an upward projecting post 37. Means is provided whereby relative adjustment can be effected the between the switch 18 and the. operating member so as to change the time at which switch is opened. Preferably the switch 18 is bodily adjustable along an arc uate path, being suitably mounted in a man nerwhich will be more fully set forth hereinafter. The disk is normally held in the position indicated in Fig. 1 by means of a spring 32. When a switch 19 is provided,-

as illustrated, the disk 29 carries an arm 30 which engages the-switch tohold it open when the diskis heldin its extreme righthand position by the-spring 32. When the a disk is rotated 1n the counter-clockwise dimotion, the post'37 engages the arm 64 of the switch 18 and forces the switch open against the resistance of a spring 65. a

For moving the operating member 29 I provide a controlling member 27 which is actua'ted by power means mechanica lly and electrlcally'independent of the motor 8 and preferably also mechanically independent of thereciprocating table 6. When the member 29 is in the form of a disk, as shown, the member 27 is in the form of a disk or wheel rotatable about the same axis. For turning the wheel 27 I preferably provide an electric motor 16 mechanically and electrically independent of the motor 8. The shaft of the motor carries a Worm 70 which meshes with worm teethformed on the pe-' I riphery of the wheel 27. Means is provided for connecting the disk 29 with the wheel 27, and, as shown, this means comprises an electro-magnet 20, one of whose terminals is connected to the supply main 11 and the other to the movable member of the switch 1. Said magnet winding is preferably mountsome friction material such as leather designed to be gripped by the disk 29 rotatably mounted on and movable vertically with the rod 23 and the core 22 as this is moved toward" and from said worm wheel.

Said disk is normally held out of engagement with the ring 28 by means by a spring 36 acting on the rod 23, although when the magnet winding 20 is energized, the magnetic flux set up therebycauses the disk to be clutched to the worm wheel the action of this spring.

As already stated, a spring 32 is provided for movin the disk 29 in the clockwise di- '80 ed in a controller box 21 and has a movable' 27 against recti'on. I his spring is indicated in Fig. 1

as beinga simpletension spring, but in, Figs. 2, 4 and 5 I have shown the form,

which I prefer, this being a coil spring surrounding the axis of the disk and having one end connected to a, suitable projection I on the partition 25. J

For limiting the movement of the arm 30 as well as gradually stopping its motion, I provide a plunger 39 operative in a suitable recess of a bracket 40 carried by the partition 25. .The plunger. is normally held in itsprojected position by a coiled spring 41. The showing of the safety switch 19 in Fig; 1 is merely diagrammatic, and as shown V of this spindle carries a block 45 from which projects a spring finger 46 electrically connected to said spindle and designed to cooperate with a terminal screw 47 also fastened to the supporting block 42. Said screw 47 likewise has threaded on it nuts 48 serving as a terminal for the connection of an electrical conductor. I mount on the spindle 43 a spring 49 whereby the block 45 and the contact finger 46 are normally held so as to [tend to move into electrical engagement with the screw 47 Projecting downward from the block 45 is a post '38 adapted to be engaged by the aforesaid arm 30 and to open the switch.

The controller box has an opening in the top in which is removably mounted a sleeve 50 constituting a bearing for a spindle 51. The sleeve has its outer end flanged to provide a circular disk 52 whose edge is notched or toothed and which is provided with a pair of stops 53 and 54 to limit the move ment of an arm 55 fixed to the outer end of said spindle so as to, move over said disk. Said arm has a longitudinally extending cavity for the reception of a plunger 57 which carries a head 56 on its outer end and holds it against the outer end of said 5 arm under the action of a spring 58 operative within the cavity. This head has a downward extending portion in which is mounted an inward projecting tooth 59 designed to coact with the teeth in the edge of 'the disk 52 with a view to retaining the arm with its connected parts in any position to which it may be adjusted. It is obvious that as the arm is turned, the head 56 may be drawn outward by means of its upward projecting knob 60 so as to clear said teeth,

flexible electrical conductors may be at-" tached. On the latter of these terminal posts is pivotally mounted a switch 'arm 64 of such length as to be capable of engaging the post 62 with which it is normally held in engagement by a spring 65. The length of this spindle and the construction of the arm or plate 61 are such that the switch arm 64 extends into the path of movement of the post 37 on the disk 29, so that the movement of thelatter causes said post to move this arm out of engagement with the terminal post 62 The top surface of: the disk 52 isegrad-uated and is marked'to indicate the amount of v feed corresponding to various positions of the arm 55 and of the switch 18. As shown, the feed can be varied from onesixty-fourth of an inch to one and threequarters inches. \Vhen the arm 55 is in contact with the stop 53 the switch 18 is moved to such a position that the arm 64 thereof is in engagement with the post 37 when the post is in its extreme right-hand position. When the arm and the switch are in this off -position, the motor 16 and the motor 8 are prevented from starting, notwithstanding the closing of the switch 2.

When the apparatus is idle, the spring 36 holds the disk 29 out of engagement with j the friction ring 28 of the worm wheel 27, so that even though the motor 16 be operated. and caused, through the worm 70 on its armature shaft, to turn said worm wheel,

this has no effect on any other part of the apparatus. Under the action of the spring 65 the arm 64 of the switch 18 engages the terminal post 62, while the disk 29 is so held by its spring 32 that the arm 30' en-' gages the post 38, holding the arm 46 of the switch 19 out of engagement with the terminal screw 47.

If it be desired that the tool head of the planer be fedimmediately after each cut is made, the dog 5 is properly adjusted on the table and the arm 55 of the controller box is moved fromits off position in engagement with the stop 53* until it is opposite that one of the graduations on the face of the disk 52 corresponding to the amount of feedto be given to the tool after each forward movement of said table. In the present instance said arm is shown as-set for a cut of about 5? of an inch and obviously the arm 61 with the arm 64 of the switch 18 likewise occupies a position correspondingly displaced from the off position.

With this arrangement of parts the table of the planer, at the completion of its forward stroke, moves the element 2 of the I pilot switch 1' into engagement with the contact 3, thus permitting currentto flow from the positive supply main 10 through the magnet winding 20, and thence to the negative supply main 11. The core 22- with the disk 29 is thus drawn down so that the latter is clutched to the worm wheel 27 and as'current is also free to flow from the, positive supply main 10 through the switches 1 and 18 to the motor 16 and to the negative supply main, the operation of said motor turns the'worm 70, the worm wheel 27 and the disk 29. Such rotation causes the arm 30 and the disk 29 to move from their ofi' positions and thus disengage the post 38, whereupon the spring 49 causes the arm 46 of the switch 19 to engage the terminal screw 47, thus completing a circuit from the positive supply main through the switch 1, terminal 47, switch arm 46 and winding I continues to turn the worm wheel 27 with.

13 to the negative main 11. The core 12 is thus raised, completing thearmature circuit of the feed motor 8, whose shunt field is at all times energized, so thatthis latter motor at once begins to feed the tool head and move the tool carried thereby.

In the meantime the control motor 16 the disk 29 until the post 37 finally comes into engagement with the arm 64 of the switch 18 and moves it out of engagement with the terminal post 62, thus breaking the circuit of said controlmotor and also that of the contactor winding 13. The core 12 is therefore allowed @to fall, thus cutting off current from the armature of the' engage the contact 3, thus cutting off cur-.

rent from the winding 20 which consequently releases the disk 29 from the worm wheel 27 The spring 32 is therefore, free to act and it at once returns the disk to its off position, permitting the arm 64 of the switch 18 to again come into engagement with the terminal post 62 and causing the armg30. to engage the post 38 and separate the contacts 46 and 47 of the switch 19. The disk 29 is ultimately'brought to rest by the spring supported plunger 39. At the end of the next forward movement of the. planer table the contact 2 of the pilot switch is again movedinto engagement with the fixed contact 3, causing the above described cycle of operations to be repeated, so that the tool head after each cutting stroke of said bed is fed through the distance determined by the adjustment of the arm 55. k f

\ Obviously the distance through which the tool head is fed may be varied by shifting the position of-said arm 55, since if it be .moved in one direction, a longer time elapses before the operation of the control motor brings the post .37 into engagement with the switch arm 64, and the feed motor 8 is thus permitted to operate for a corre-' spondinIgly longer period to shift the tool head. f said arm 55 be moved in .the op- 'posite direction, the arm 64 of the switch 18 is sooner engaged by the post 37 and the feed motor is put out of operation after it has moved the tool head through a correspondingly less distance.

for causing the opening of the By providing the safety switch 19, I re- Vent the possibility of the accidental starting of the feed motor'8 in case the switch 18 after once being opened, is permitted to close while the switch is still closed. Such a closing of the switch 18 might be caused by a possible slipping of the clutch provided by the disk 29 and worm 27 or by the open circuiting of the winding 20. Obviously under these conditions the spring 32 at once turns the disk 29 into such position that its arm 30, by engaging the post 38, opens the switch 19.

Mechanisms have heretofore been proposed in which the feed motor is operatively connected with a limitswitch so that the motor acts to stop itself after movement to a predetermined extent. In mechanisms of this sort it has been difficult to provide for the adjustment of the amount of travel, particularly when the motor is arranged to be operated always in the same direction without reversal.v Furthermore, even when an adjusting means has been provided, it has been found that it was difiiqult to start the motor and thereafter stop it quickly enough to provide for the small feeds which are very frequently necessary. The feed motor necessarily moves relatively slowly, particularly when the desired feed is so small as not to allow the motor time to acquire its normal speed. The result has been that with limit switches operated by the feed motor itself it was impossible to secure the fineness of adjustment which is necessary for very small feeds.

In accordance with my invention, the stopping of the feed motor is effected entirely independently of the motor itself, and in this way the difiiculties above" referred to are avoided. The supplementa "motor 16 and the parts connected therewitl" aresmall and light and can be very quicklyset in motion. While the'relatively largemotor 8 is making a fraction of a revolution, as may be necessary for a' very small feed, the smaller and lighter motor 16 may make several revolutions and thus eifect'the opening of the circuit for the feed motor to stop the motor.

I claim 1. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head, table operated means for causing the closing of the circuit of the motor at each reciprocation, and movable means mechanically and electrically independent of the motor circuit of the motor after a predetermined interval.

2. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head, table operated means for causing the closing of the circuit of the motor at each recipof the circuit of the motor at each reciprocation, and movable means mechanically independent of the table and mechanically and electrically independent of the motor for causing the opening of the circuit of the motor after a predetermined interval.

4. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head, a relay switch for closing and opening the circuit of the motor to start and stop it; a

table operated switch for closing the relay circuit to start the motor at each reciprocation. and a switch operated independently of the motor for opening the relay circuit to stop the motor after a predetermined interval.

i 5. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head, table operated means for causing the closing of the circuit of the motor at each reciprocation, and an electric motor mechanically independent of the table and mechanically and electrically independent of the feed motor for causing the opening of the circuit of the feed motor after a predetermined interval.

6. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head, an electric motor mechanically independent of the table and mechanically and electrically independent of the feed motor for causing the opening of the circuit of the feed motor after a predetermined interval and, table operated means for causing the closing of the circuit of the feed motor at each reciprocation of the tabie and for starting the in dependent motor.

7. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head, an electric motor mechanically independent of the table and mechanically and electrically independent of the feed motor for causing the opening of the circuit of the feed motor after opening its own circuit, and table operated means for causing the closing of the circuit of the feed motor at each reciprocation of the table and for starting the independent motor.

8. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head,

table operated means for causing the closing of the motor circuit to start the motorat each reciprocation, an electric motor mechanically independent of the table and of the feed motor, an operating member driven by the said independent motor, and means for causing the stopping of the feed motor after movement of the said operating member to a predetermined extent.

9. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head, table operated means for causing the starting of the motor at each reciprocation, an electric motor mechanically independent of the table and of the feed motor, an operating member driven by the said independent motor, and means for causing the stopping of the feed motor after movement of the said ope-rating member to a predetermined extent and for simultaneously causing the stopping of the independent motor.

10. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head, a table operated switch for causing the starting of the motor at each reciprocation, an operating member operated independently of the motor for causing the stopping of the motor after a predetermined interval, and a second switch in series with the table operated switch and automatically closed by the operatingmember at the beginning of its movement.

11. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head, a switch in the controlling circuit of the motor, a table operated switch connected in series with the first said switch, an operating member operated independently of the motor for opening the first said switch after movement to a predetermined extent, and means whereby the operating member is started upon the closing of the last said switch.

12. The combination with a reciprocating planer table and a movable tool head, of an electric motor for feeding the tool head, two switches connected in series in the controlling circuit of the motor, an operating member operated independently of the motor for closing one of the switches and after a predetermined interval opening the other,

'a third table operated switch connected in connecting the operating member to the controlling member for movement therewith, and adjustable means for stopping the motor includin a switch operated by the operating mem er aftertravel to any desired extent.

14. In a motor controlling system, the combination of an electric motor, a controlling member actuated independently of the motor, an operating member, means for starting the motor and for simultaneously connecting the operating member to the controlling member for movement therewith, and a bodily adjustable'switch for stopping the motor, the said switch being operated by the operating member after travel to any desired extent.

15. In va motor controlling system, the

combination of an electric motor, a movable controlling member mechanically and electrically independent of the motor, an operating member, means for starting the motor and for simultaneously connecting the operating member to the controlling member for movement therewith, and means for stopping the motor and for simultaneously stopping the controlling member, the

. said means being operated by the operating member after travel to a predetermined extent.

16. In a motor controlling system, the combination of an electric motor, a movable controlling member mechanically and elec combination of an electric motor, a controlling member actuated independently of the motor, an operating member automatically movable to an ofi' position, means for starting the motor and for simultaneously connecting the operating member to the controlling member' for movement therewith away from the offposition, the said means subsequently permitting the-disconnection of the operating and controlling members whereupon the operating member returns to the off position, and means for stopping the motor, the said'means being operated by the operating member after travel to a predetermined extent away from the 011" position.

18. In amotor controlling system, the

combination of an electric motor, a movable controlling member mechanically and elec trically independent of the motor, an operating member, a magnetically actuated clutch interposed between the controlling member and the operating member, a switch for starting the motor and for energizing ling member actuated independently of the motor, an operating member automatically movable to an off position, a magnetically actuated clutch interposed between the controlling memberand the operating member, a switch for starting the motor and for energizing the clutch to connect'the operating member to the controlling member for movement therewith, the said switch subsequently serving to denergize .the clutch whereupon the operating member returns to the off position, and avswitch for stoppingthe motor and for simultaneously stopping the controlling member, the said switch being operated by the operating member after travel to a predetermined extent.

20. In a motor controlling. system, the combination of an electric motor, a controlling member, a second electric motor mechanically and electrically independent of the first motor for actuating the controlling member, an operating member, means for starting both motors and for simultaneously connecting the operating member to the controlling member for movement therewith, and adjustable means for stopping the first said motor, the said means being operated by the operating member after travel to any desired extent. I

21. In a motor controlling system, the combination of an electric motor, a controlling member, a second electric motor independent of the first motor for actuating the controlling member, an operating member, a

magnetically actuated clutch interposed between the controlling member and the operating member, a switch for starting both motors and for energizing the clutch to connect the operating member to the controlling member for movement therewith,

and a switch for stopping the first said motor, the said switch being operated by the operating member after travel to a predeter-- mined extent.

22. In a motor controlling system, the combination of an electric motor, a controlling member, a second electric motor independent of'the' first motor for actuating the controlling member, an operating member, a magnetically actuated clutch'interposed between the controlling member and the operating member, a switch for starting both motors and for energizing the clutch to connect the operating member to the controllingmember for movement therewith, and

a switch for stopping both motors, the said switch being operated by the operating ,a switch controlling the operation thereof;

a second motor mechanically and electrically independent of the first motor for operating said switch; and a magnetically actuated clutch interposed between the second motor and said switch; with an automatically actuated switch for governing the operation of said clutch.

24. In a motor controlling system, the combination of an electric motor, a controlling member, a second electric motor independent of the'first motor for actuating the controlling member, an operating member automatically movable to an off position, a magnetically actuated clutch interposed between the controlling member and the operating member, a switch for starting the 'motor and for energizing the clutch to connect the operating member to. the controlling member for movement therewith, and

' a switch for stopping the motor, the said switch being operated by the operating member after travel'to a predetermined extent and the said operatingmember subsequently returning to off position upon the opening of the first said switch.

25. The combination in a current controlling system of two relatively adjustable structures; a switch on one structure; a device for operating the switch on the other structure; a motor connected to actuate one of the structures to operate the switch; with a second switch mounted to be operated by the motor actuated structure after the first switch Has been operated.

26. The combination in a current controlling systtm of a switch; an operating device therefor; a motor for causing said device to operate the switch; a magnetically actuated clutch interposed between the motor and said device; and a second switch mounted to be actuated by the motor-operated member after said clutch has been ,deEinergized. Q

27. The combination in a currentcontrolling system of a switch; an operating device therefor; a motor for causing said device to actuate the switch; a magnetically actuated clutch interposed between the motor and said device; a second switch mounted to be actuated by the motor-operated mem ber after said clutch has been denergized; with an automatically actuated switch for controlling the flow of current to the clutch.

28. The combination in a current controlling system of a rotatably mounted switch;

a rotatably mounted member, for operating said switch; means tending to maintain said member in a definite position; a motor for moving said member from said position to open the switch; with a second switch mounted to be acted on by the member when it" is adjacent said position. I

29. The combination of an electric motor; a switch in the controlling circuit of the motor; a movably mounted member for operating the switch; means normally holding said member in a definite position; a motor mechanically and electrically independent of the aforesaid motor for moving said member from said position to open the switch; and means for automatically disconnecting said member from the independent motor under predetermined conditions.

30. The combination of a switch; a movably mounted member for operating said switch; a spring normally holding the member in a definite normal position; a motor for moving said member from such position to operate the switch; a clutch interposed between the member and said motor;

and a second switch normally held in an open position when said clutch is released.

31. The combination of aswitch; a rotary member for operating the same; means for normally holding said member in a ldefinite position; a motor for moving the member from said position to open the switch; means for adjusting the position of said switch to vary its angular "distance from said member; a magnetically actuated clutch interposed between the motor and the member; and a second switch mounted to be operated by the member after said clutch has released it from the motor.

32. The combination of a motor; a switch in the controlling circuit of the motor; a member for actuating the switch; a motor mechanically and electrically independent of the first said motor for operating said member from a normal position to cause it to open'the switch; and means for automatically disconnecting the member from the independent motor after the switch has been opened. I 33. The combination of a motor; a switch in the controlling circuit of the motor; a member for actuating the switch; a motor mechanically and electrically independent of the first said motor for operating said member from a normal position to cause it to open the switch; and means independent of the second said motor for automatically returning said member to its normal position after it has opened the switch.

T mbination of a feed motor; a switch controlling the operation thereof; a member for opening said switch; a second motor for actuating said member; means for varying the time elapsing between the starting of the second motor and the opening of said switch; 'a clutch; a second switch in circuit with the feed motor; and means for holding the latter switch open when the clutch is released.

35. The combination of a support; a structure rotatably carried thereby; a normally closed switch mounted on said structure; a rotary switch-operating member; means for angularl'y adjusting the position of the switch relatively to sald member; a

motor for turning the member toward the 10 switch from a normal position; a magneti- 'cally actuated clutch between the member and the motor; aspring tending to hold said member in a definite position; with a second switchin circuit with the first switch 15 and mounted to beheld open by said mem her when this is in said normal position.

SVEN P. JOHNSON. 

